The rhesus macaque as an animal model for hemophilia B gene therapy.
We have determined the 2905 nucleotide sequence of the rhesus macaque factor IX complementary DNA (cDNA) and found it to be greater than 95% identical to that of the human factor IX cDNA. The cDNA has a large 3' untranslated region like the human cDNA, but unlike the human cDNA has two polyadenylation sites 224 nucleotides apart that are used for transcription of the messenger RNA. The deduced amino acid sequence is greater than 97% identical to that of human factor IX, differing in only 11 of 461 amino acids in the complete precursor protein. We found a single silent polymorphism in the nucleotide sequence at the third position of the codon for asparagine at position 167 in the secreted protein (AAC/AAT). All residues subject to posttranslational modifications in the human protein are also found in the rhesus factor IX sequence. The high degree of homology between the rhesus and human factor IX proteins suggested the possibility that the human factor IX protein might be nonimmunogenic in the rhesus. We tested the immunogenicity of human factor IX in three rhesus macaques by repeated intravenous injections of monoclonal antibody-purified, plasma-derived human factor IX over the course of more than a year and assessed the recovery and half-life of the infused protein, as well as in vitro indicators of antihuman factor IX antibodies. Human factor IX recovery and half-life remained unchanged over the course of a year in the three animals studied, and aPTT mixing studies showed no evidence for neutralizing antihuman factor IX antibodies. An outbred, nonhuman primate model that permits assessment of the level and duration of factor IX expression as well as vector safety would complement the use of other (mouse and canine) hemophilia B animal models in current use for the development of gene therapy for hemophilia B. (+info)
Sustained correction of bleeding disorder in hemophilia B mice by gene therapy.
Mice generated by disrupting the clotting factor IX gene exhibit severe bleeding disorder and closely resemble the phenotype seen in hemophilia B patients. Here we demonstrate that a single intraportal injection of a recombinant adeno-associated virus (AAV) vector encoding canine factor IX cDNA under the control of a liver-specific enhancer/promoter leads to a long-term and complete correction of the bleeding disorder. High level expression of up to 15-20 microgram/ml of canine factor IX was detected in the plasma of mice injected with 5.6 x 10(11) particles of an AAV vector for >5 months. The activated partial thromboplastin time of the treated mice was fully corrected to higher than normal levels. Liver-specific expression of canine factor IX was confirmed by immunofluorescence staining, and secreted factor IX protein was identified in the mouse plasma by Western blotting. All treated mice survived the tail clip test without difficulty. Thus, a single intraportal injection of a recombinant adeno-associated virus vector expressing factor IX successfully cured the bleeding disorder of hemophilia B mice, proving the feasibility of using AAV-based vectors for liver-targeted gene therapy of genetic diseases. (+info)
Persistent expression of canine factor IX in hemophilia B canines.
We previously demonstrated that direct intramuscular injection of recombinant adeno-associated virus (rAAV) carrying the human FIX (hFIX) cDNA can safely be administered to hemophilic B canines and express human factor IX protein; however, the functional activity of the hFIX protein could not be assessed due to anti-human FIX antibody (inhibitor) formation. To test the therapeutic efficacy of rAAV in hemophilic dogs, rAAV type 2 (rAAV2) carrying canine FIX (cFIX) cDNA was injected into the skeletal muscle of two dogs at doses of 1012-13particles. Circulating cFIX protein levels were maintained for 1 year at levels of 1-2% of normal. Hemostatic correction (WBCT and APTT) paralleled plasma FIX antigen levels. Both dogs still required plasma infusion for spontaneous and traumatic bleeding events. Inhibitors to cFIX protein were not detected in either animal by Bethesda assay. Neutralizing antibodies directed against AAV-2 capsid were pronounced and persistent. Vector DNA and mRNA transcripts were detected only at the injected skeletal muscle tissue. Analysis of both high and low molecular weight DNA identified both replicative episomal and integrated AAV species. These results demonstrate that persistent secretion of the FIX transgene protein, necessary for successful gene therapy of hemophilia B, can be achieved using the parvovirus-based rAAV vector (+info)
Mutation rates in humans. I. Overall and sex-specific rates obtained from a population study of hemophilia B.
A population-based study of hemophilia B mutations was conducted in the United Kingdom in order to construct a national confidential database of mutations and pedigrees to be used for the provision of carrier and prenatal diagnoses based on mutation detection. This allowed the direct estimate of overall (micro), male (v), and female (u) mutation rates for hemophilia B. The values obtained per gamete per generation and the 95% confidence intervals are micro;=7.73 (6. 29-9.12&parr0;x10-6; v=18.8 (14.5-22.9&parr0;x10-6; and u=2.18 (1. 44-3.16&parr0;x10-6. The ratio of male-to-female mutation rates is 8. 64, with a 95% confidence interval of 5.46-14.5. The higher male rate was not caused by a much higher rate of transition at CpG sites in the male. Attempts to detect evidence of gonadal mosaicism for hemophilia B mutation in suitable families did not detect any instances of ovarian mosaicism in any of 47 available opportunities. This suggests that the risk of a noncarrier mother manifesting as a gonadal mosaic by transmitting the mutation to a second child should be <0.062. (+info)
Mutation rates in humans. II. Sporadic mutation-specific rates and rate of detrimental human mutations inferred from hemophilia B.
We estimated the rates per base per generation of specific types of mutations, using our direct estimate of the overall mutation rate for hemophilia B and information on the mutations present in the United Kingdom's population as well as those reported year by year in the hemophilia B world database. These rates are as follows: transitions at CpG sites 9.7x10-8, other transitions 7.3x10-9, transversions at CpG sites 5.4x10-9, other transversions 6.9x10-9, and small deletions/insertions causing frameshifts 3.2x10-10. By taking into account the ratio of male to female mutation rates, the above figures were converted into rates appropriate for autosomal DNA-namely, 1.3x10-7, 9.9x10-9, 7.3x10-9, 9.4x10-9, 6.5x10-10, where the latter is the rate for all small deletion/insertion events. Mutation rates were also independently estimated from the sequence divergence observed in randomly chosen sequences from the human and chimpanzee X and Y chromosomes. These estimates were highly compatible with those obtained from hemophilia B and showed higher mutation rates in the male, but they showed no evidence for a significant excess of transitions at CpG sites in the spectrum of Y-sequence divergence relative to that of X-chromosome divergence. Our data suggest an overall mutation rate of 2.14x10-8 per base per generation, or 128 mutations per human zygote. Since the effective target for hemophilia B mutations is only 1.05% of the factor IX gene, the rate of detrimental mutations, per human zygote, suggested by the hemophilia data is approximately 1.3. (+info)
Molecular analysis of hemophilia B in Poland: 12 novel mutations of the factor IX gene.
We examined the molecular basis of factor IX deficiency in 53 unrelated Polish patients with hemophilia B. Heteroduplex analysis and direct sequencing of polymerase chain reaction (PCR) products were applied to identify the gene defect. Forty-three different point mutations were detected in the factor IX gene of 47 patients. There were 29 missense mutations, 9 nonsense mutations, 4 splice site mutations and 1 point mutation in the promoter region. Twelve mutations were novel. The results of this study emphasize a very high degree of heterogeneity of hemophilia B. (+info)
Experience of a single Italian center in genetic counseling for hemophilia: from linkage analysis to molecular diagnosis.
BACKGROUND AND OBJECTIVE: We describe our three year experience in genetic counseling at the Castelfranco Veneto Hemophilia Center, Italy. DESIGN AND METHODS: A total of 258 individuals were involved in the study of 142 females. These formed 40 families with hemophilia A and 6 families with hemophilia B. Following pedigree analysis, the FVIII inversion was first examined in severe hemophilia A patients by polymerase chain reaction (PCR) analysis. DNA polymorphisms were used to track the affected gene through the remaining families. In uninformative cases, we initiated analysis of the FVIII or FIX gene coding region by conformation sensitive gel electrophoresis and DNA sequencing to identify the mutation responsible for the disease. RESULTS: The FVIII gene inversion was present in 16 of the 32 patients (50%) affected by severe hemophilia A and was informative for 44 females. For hemophilia A, 45 cases (55%) were informative by linkage analysis, however 37 (45%) were uninformative because of lack of key individuals, homozygosity, or sporadic disease. Information from extragenic linked polymorphisms alone was present in 9 cases (6%). For hemophilia B, linkage analysis was informative in only 50% of females (8 out of 16). To date, nine mutations have been identified in patients with hemophilia A and three in patients with hemophilia B. Six novel missense mutations in hemophilia A are discussed briefly. INTERPRETATION AND CONCLUSIONS: Using this approach we are now able to offer accurate genetic analysis to virtually all families with hemophilia. (+info)
Simple screening tests for the diagnosis of isolated clotting factor defects. With special reference to 'contact factor' defects.
Reagents may be prepared from normal plasma and used with the prothrombin time and partial thromboplastin time tests to distinguish isolated defects of factors I, II, VII, VIII, IX, X, XI, or XII. (+info)